In German Democratic Republic Pat. No. 238,102 German Democratic Republic patent application No. WP F 27 D/315 174-7, and U.S. Pat. No. 4,775,315, machines are presented for breaking out deposits and the lining of rotary kilns. The two machines are characterized in that, while the tubular cylinder of the rotary kiln rotates about its own center line, the breaking out of deposit and lining takes place together or separately by means of a pounding, wedging or breaking action. These known technical solutions are particularly suitable for applications, in which solid and stressed linings and deposits of appropriate thickness in rotary kilns are broken out by the selective destruction of their arched structures. When used for thin, soft or tough layers of deposits of the incrustation, and also when very loose material is to be removed, the method and the associated apparatus, cannot guarantee an economic mode of operation, because of their pounding, coarse, wedging mode of operation. The result, aimed at the pounding action, shows an intensive, point-like stress on the cylinder jacket or the elements of the apparatus, since the material that is to be worked on is soft, or tough, and offers a latent resistance to the impacting action of the apparatus. It is also disadvantageous that the construction and equipment costs are very large to build the apparatus with a pounding action.
U.S. Pat. No. 3,245,154 discloses an apparatus for distributing solid, flowable, adhesive or sludge-like materials in a rotary drying kiln during the drying process to avoid caking. This apparatus achieves its effect by a rolling friction on the inner wall of the drum. This apparatus consists of three parts. On the one hand, it consists of two different sectors, the external diameters of which are equal to the internal diameter of the drum. They are fastened in the drum and have no sliding contact lines with the drum. The third sector of the apparatus, as does the second sector, consists of lifing bars, the outer edges of which are directed radially towards the inside of the drum. This third sector has an external diameter, which is smaller than the internal diameter of the drum and moves radially rolling and axially guided in the drum. As the drum rotates, this third sector is moved into a suspended position. As it rolls back from this position, it produces with the outer edges of its lifting bars contact lines on the inside of the drum.
The material, sliding into the drum over a discharge hopper, passes through the apparatus, starting with the third sector. Only the outer edges of the lifting bars of this sector, which takes up the material, rub on the inside of the drum. The only function of the lifting bars with their tongues and with the furthermore provided feeding bars in the second and in the first sector is to transport the material.
The object of the U.S. patent and the means of accomplishing this object are as follows: to keep an amorphous material uniformly distributed and mobile as it passes through a drum during a drying cycle. With the disclosed apparatus, which was described above, the material is lifted from the wall of the drum and held loose and guided to the outlet of the drum by means of parts of the apparatus.
U.S. Pat. No. 3,333,837 discloses a drum, which rotates about a generally horizontal axis and in which there is disposed a cage, which can be rotated parallel to the axis of rotation. The roll diameter of the cage is less than the internal diameter of the drum and its length is congruent with that of the drum. The cage consists of an open frame, which has radially directed working elements, which are distributed uniformly over its periphery and form sliding contact lines on the inside of the drum. The working elements are formed in a further development of the apparatus.
In the cage, chains are suspended, with are connected with the working elements. The rotation of the drum moves the apparatus into a suspended position, from which it returns with a rolling motion or in which it can also stay with a rolling motion. During the rolling process, the outer edges of the working elements rub on the drum and lift introduced material up from there and then transport this detached material onward.
The object and the mode of action of the solution of the patent are similar to the solution set forth in U.S. Pat. No. 3,245,154 for the applicable third section. The solution of this patent shows a one-piece apparatus with working elements, which are constructed as a cage on its body, are aligned essentially radially, rub by a rolling action in the drum and avoid caking from the very start. The rubbing and scratching action of the working elements on the inside of the drum is intensified further, if the working elements, disposed on the cage, have a helical shape. No provisions are made for an axial motion of the cage in the drum.
U.S. Pat. No. 3,607,399 discloses a method and an apparatus for detaching and removing felted matter and collections of fiber materials from the inner wall of drums, in which these fiber materials are to be dried. The fiber material is blown with a current of carrier air into the rotary drier and moved about and dried in this drier.
At least two rolling working elements are provided in the drum to prevent accumulations generally by felting of the fiber material. These working elements are constructed as rollers and extend the whole length of the inside of the drum. One of the rollers, the heavier one, has a driving function with respect to the second roller, which has a cleaning function, and is situated immediately in front of the second one with respect to the direction of rotation of the drum. THe driving roller has a frictional rubber surface. The surface of the second roller, the actual cleaning roller, has cleaning elements, which simultaneously adhere to the surface of the driving roller and of the inner wall of the drum. The static friction between the rollers is intensified further owing to the fact that the cleaning roller, due to its disposition behind the driving roller with respect to the direction of rotation of the drum, is constantly forced by this driving roller into a suspended position. The cleaning roller has a larger external diameter than the driving roller and therefore a faster circumferential velocity. It works on the inner wall of the drum with a scratching and rubbing action. Due to the arrangement of the driving and cleaning rollers, the rubbing action is restricted to material, which adheres during one revolution. Firmly adhering, compact material cannot be removed.